1. Field of the Invention
The present invention relates to orthopaedic implants, and, more particularly, to provisional implants used to check, align, mark, cut, etc. various surfaces on a bone.
2. Description of the Related Art
During a revision knee surgery, the primary implant is removed from the distal end of a femur and a revision implant is replaced on the distal end of the femur. A provisional implant is commonly used during revision surgery after the old primary implant is removed to provide a visual indication to the surgeon that the new primary implant will properly fit the reshaped bone and function properly. Since many of the anatomical landmarks which are present during a primary surgery no longer exist during a revision surgery, the provisional allows a surgeon to visually orient and align the implant. The provisional implant performs the dual function of a cutting guide and, therefore, may include a plurality of bone pin openings, saw guides, and/or threaded openings allowing attachment to and shaping of the distal end of the femur.
It is advantageous to align the joint line between the new femoral component and tibial component with the patella implant, since in many cases the patella is the only anatomical landmark that remains after the primary implant is removed. It is known that the patella implant may be located relative to the joint line defined by the articulating surface of the provisional implant so that the patella implant properly interfaces with the revision implant. Typically, a surgeon simply estimates the femoral and tibial component location relative to the patella or preforms a trial reduction to visually determine if the placement of the components is correct relative to the patella. Placement of the femoral and tibial components relative to the patella implant is subject to parallax and alignment errors by the surgeon, and is inconsistent, which may lead to a less than optimal performance of the prosthetic knee after implantation.
What is needed in the art is a surgical technique using orthopaedic instrumentation which consistently and accurately allows a femoral provisional component to be located relative to the patella.